Electrostatic sound reproducer



June 9, 1931. -J. B. HAWLEY ELECTROSTATIC SOUND REPRODUCER Filed March 7, 1928 Mld - Je .E

Patented June 9, 1931 UNITEn STATES PATE NT oFFlcE JESSE s. HAWLEY, or sncH'ARLEs, ILLINoIs, AssIGNon I.ro UNITED'REPRODUCERS PATENTS conPoRA'rroN, or sr. CHARLES, ILLINOIS, A CORPORATION' 0E NEVADA ELECTROSTATIC SOUND REFRODUCR Applicationv anni umh 7,

The present invention relates to sound reproducers such as 'those used in radio re' ception and has reference more particularly tothe type known as electro-static sound producers and reproducers.` It is regarded as an improvement of-that disclosed in the patent to Colin Kyle, No. 1,644,387, grantv@d october 4, 1927.

mitting medium, such as air. The surfaces of the depressions or the regions sui'ound-V ing the openingsV or apertures arepreferably inclined or recede gradually from thel main surface or the crest portions of the plate, suchsurface blending with such main surface or crest surface portions.

ln normal contact with the'main surface' of the plate or the crests thereof is a dielectric member, such as a sheet or`thin'mat`erial as for example, such as rubber, rub-y berized fabric, and other likeand similar dielectric materials. Such dielectric mem- 4ber is preferably stretchedA over the sur-v -face of the plate with such tension `that the portions of the dielectric member lo cated opposite 'the depressions Vor troughs may fiex .under electro-static attraction, and

enter the depressions or` troughs in such manner that the dielectric member will come into contact with the inclined or receding surface portions of such depressions or troughs, the surface portions juxtaposedor proximate to the main surface: or crest portions of the plate first beingcontacted and then the more remote portions of said surfaces. The altitudes or depths of the 1928. Serial No. 259,717.

lowest audible tones orvsound waves of lowest frequency in the audible range of sound.

The opposite side of the dielectric is pref- ;erably coated with a conducting surface or.

material or foiled withsuch metals as gold leaf, silver leaf, valuminum foil, and other like and similar foils.

Other objects, capabilities, advantages .and features are comprehended by the in vention as will later appear and are inherently possessed thereby. 'J Referring to the ldrawings, Fig. l is a view in vertical elevation of a` sound reproducer constructed in accordance with the invention, with parts shown broken?t away; Fig. 2 -is a fragmentary sectionall view .through a part of the device, and showing the dielectric member and' foiled surfacev in normal positiongFig. V3 is a similar 'view showing the dielectric and foil lexed into a depression F ig. 4 is a similar 1a dielectric member 5 which may be of any suitable dielectric material, such as rubber, rubberlzed fabric,and other like and similar materials. On 'the surface of the dielectric 5 opposite from that contacting with the plate 3, is attached a flexible metal surfacev such as gold leaf 6, silver leaf, aluminum foil, and the like and similar foils.

Referring to Fig. 2, the :plate 3 is shown as provided-with a depression 7, having a curved'surface 8 receding gradually from the main surface 9 of the plate and extending toward the opening 4. In this form, the depression'or trough is concaved as shown, and the annular wall thereof is of approximately ogee form in longitudinal section. Normally, the dielectric 5 and the foil 6 on the back thereof, occupy the position shown in Fig. 2, but when electro-static attraction is effected, that portion of the-dielectric opposite the depression will be caused to fiex and enter more or less, depending upon the amount of attraction, into the space of the depression, such as that shown in Fig. 3. It will be noted -that the dielectric nearer to the upper part of the inclined surface 8 will first be attracted to the surface 8 thus bringing adjacent portions of the dielectric nearer to adjacent portions of the surface 8, and thus progressively bringing the dielectric into proximity with such surface in succession from the surface portions nearest the main surface portion 9 of the plate until more remote portions are brought into contact by the dielectric. While this has been described as successive, it will be understood that the action is so rapid that it is almost instantaneous. The effect is to bring the dielectric surface into the position such that it will be nearer to the surface attracting it as the electrostatic action is effected to cause `stantial extent into the depression.

movement of the dielectric. The surface 8 recedes' gradually from the surface 9 and the depressions may be of any'suitable design or form, that shown in Fig. 2 being of the circular concave shape. Hence, it will be seen that the successive contacting areas of the dielectric with the surface 8 will be annular or ring form.

Fig. 3 shows the dielectric flexed to a sulli- T e depth ofthe depressions or troughs is at least as great as and preferably greater than the maximum amplitude of vibration of the 'dielectric for the lowest tones of the audible range of sound, in order that the device may operate efficiently.

In the form shown in Fig. 4, the depression 7 is made inthe form of a hollow cone instead of a concaved or rounded part. In

. other respects, the structure is similar to that described above and shown in Figs 2 and 3. Y'

In Fig. 5, the plate is shown with rounded ridge or crest portions 9a, and curved or -concaved depressions or trough portions 7b.

The troughs may be made of any form desired, such as the depressions shown in Figs. 2, 3 and 4 or may be made in the form of corrugations with intervening crest portions 9a. In this particular form, the normal contact with the plate will be upon very narrow areas or regions of the crests 9, `and practically all of the electro-static action will be effected by the bringing of the dielectric more or less into. proximity with the curved surfaces of the troughs running from the crest 9a.

In all 'of the forms described, the depth of the depression is less than its greatest diameter, so that a substantial part of the contiguous portion of the diaphragm will flex inwardly into contact with the adjacent portion of the inner surface of the wall of thc depression. In operation, the plate is connected to one side of a. circuit and the foil is connected to the other side whereby changes in potential in the circuit may effect corresponding electro-static attractions and repulsions to cause the dielectric to flex and vibrate the surrounding air or other sound transmitting medium. The efficiency of the device is greatly increased by the use of the depressions and troughs above described in the manner of flexing the dielectric such as to bring the same into close contact with the attracting surface of the depressions, so that a greater electro-static effect may be produced by reason of moving the dielectric into closer contact and thus bringing the foil closer to the plate. In experiments with this type of device, it has been found that the faithfulness of sound reproduction has been made practically perfect with beautiful tcie effects,

lVhile I have hereindescribed and upon the drawings shown preferred embodiments of the invention, it is to be understood that the latter is not limited thereto but may comprehend other constructions, arrangements of parts, details, and features without departing from the spirit thereof.

Having thus disclosed the invention,

I claim:

1. An electrostatic sound producer com- Vprising an electro-conductive plate provided with a depression having its upper` edge gradually merging into said plate, and having a central opening in its bottom portion,

said depression gradually diminishing in diameter from the top to the bottom thereof, a flexible dielectric diaphragm engaging said plate and covering" said opening, the depth of said depression being less than its greatest diameter, so that a substantial part of the contiguous portion of the diaphragm w1ll flex inwardlyinto contact with the adj acent portion of the inner surface of said depression, and means providing a conducting surface on the outer face of said diaphragm.

2. An electrostatic sound producer comprlsing an electro-conductive plate provided with a depression having its upper edge gradually merging into said plate, and having a central opening in its bottom portion, the wall of said depression bein of approximately ogee form in longitu inal section, so that the de ression gradually diminishes in diameter om the top to the bottom thereof, a fiexible dielectric diaphragm engaging said plate and covering said depression, the depth of said depression being less than its greatest diameter, so that a substantial part of the contiguous portion of said diaphragm will flex inwardly into contact with the adjacent portion of the inner surface of said depression, and means providing a conducting surface on the outer face o'f said diaphragm.

3. An electrostatic sound producer comprising an electro-conductive plate having rounded ridges and also having depressions on both sides of said ridges, each depression having its upper edge gradually merging into said ridges, and having a central opening in its bottom portion, said depressions gradually diminishing in diameter from the tops to the bottoms thereof, a tiexible dielectric diaphragm engaging said plate and covering said openings, the depth of each depression being less than itS greatest diameter, so that substantial parts of contiguous portions of said diaphragm Will Hex inwardly into contact with the adjacent portions of the inner surfaces of the depressions, and means providing a conducting surface on the outer face of said diaphragm.

4. An electrostatic sound producer comprising an electro-conductive plate provided with rounded ridges and having spaced apart depressions on opposite sides of said ridge, each depression having its upper edge gradually merging into the contiguous ridges, so that the wall of each depression is of approximately ogee form in longitudinal section, each depression having a central opening in its bottom portion and gradually diminishing in diameter from the top to the bottom thereof, a flexible dielectric diaphragm engaging said plate and covering said openings, the depth of each depression being less than its greatest diam- V eter, s0 that substantial parts of contiguous portions of said diaphragm will flex inwardly into contact with the adjacent portions of the inner surfaces of the respective depressions, and means'providing a conducting surface on the outer face of said diaphragm.

In Witness whereof, I hereunto subscribe my name to this specification.

JESSE B. HAWLEY. 

